1. Field of the Invention
This invention involves a grate bar for grate linings, especially in furnaces, which exhibits lateral contact surfaces and external ribs.
2. Description of the Prior Art
In a known grate bar of this type (DE-PS No. 959212), the lateral contact surfaces are machined for reasons of sealing and friction reduction. These contact surfaces project above the external ribs along one part of the grate bar's length, so that only small surfaces need to be machined. The front of the bar contains a jet-like air channel which is formed by a recess in at least one lateral contact surface between adjoining bars. Air enters the burning layer situated above the grate lining through this air channel from the area beneath the grate after being forced through the grate bar.
Small particles from the burning layer may lodge in this air channel between adjoining external ribs of the grate bars, which are separated by a narrow interval. The intruding particles tend to separate the adjoining grate bars, causing the air supply forced through the hollow bars to be disturbed, since air can stream directly from the space beneath the grate into the combustion chamber between the resulting gap. This can lead to reduced air movement in the affected bars and consequently to overheating and increased wear. Such particles may also block the reciprocal travel of adjoining bars due to enlarged gaps, even if they do not cause wear despite the relative displacement of adjoining bars.
Since the lateral contact surfaces are subject to natural wear after extended operation, the space remaining under the air channel between the external ribs of adjoining bars gets progressively smaller, so that particles falling into the air channel remain suspended in this area and contribute to the operating faults described above.
The invention is designed to avoid the possibility of disturbances in the narrow space under the air channel due to jamming of particles escaping into the air channel, even when the lateral contact surfaces show increased wear; that is, it fashions the grate bar in such a manner that the particles entering the air channel are rapidly removed from the space beneath the air channel between the bars, even up increased wear of the contact surfaces, so that they are prevented from jamming between adjoining bars and from increasing the interval between adjoining bars. In particular, the hollow core cooling of the grate bar (in the case of bars with hollow cores) should not suffer undue interference.